From the end of the last bread:
This is how POTUS activates EAS
The national-level EAS is activated by an order from the President to the White House Communications Agency (WHCA) duty officer or the President’s Communications Officer (PCO) through the FEMA Operations Center (FOC) or FEMA Alternate Operations Center (FAOC). The FOC/FAOC authenticates the request and establishes the Primary Entry Point (PEP) conference. At the request of the President, FEMA distributes Presidential Level messages to the PEP stations. As the entry point for national-level EAS messages, the PEP stations have a National Primary (NP) EAS designation and are monitored in turn by other AM and FM radio stations; TV broadcast stations (audio only) and cable systems (audio only) in the hierarchical chain. The 83 National Primary PEP stations are listed in figure E.1.'
Attaching NAWAS manual that has a ton of good info including list of PEP stations which are battle hardened for this purpose.
PEP stations can be an important destination in the event of a catastrophe.